The director of 'Creed 2' explains the movie's emotional ending — and shares the line Sylvester Stallone came up with on the spot

"Creed II" director Steven Caple Jr. explains what led to the emotional ending.

He also shares the line Sylvester Stallone came up with on the spot at the conclusion of the final fight.

Warning: Spoilers below if you haven't seen "Creed II."

"Creed II" has quickly become a critical and box-office success thanks to the movie touching on the "Rocky" franchise mythology — specifically Adonis Creed (played by Michael B. Jordan) facing the son of Ivan Drago, who was responsible for Apollo Creed's death in "Rocky IV" — while also delving deeper into the storylines of Adonis and Rocky Balboa (Sylvester Stallone).

That is especially evident in the movie's ending, which doesn't close with a dramatic fight, as many of the "Rocky" movies did, but with an emotional dive into the main characters.

For the Dragos, Ivan (Dolph Lundgren) and his son Viktor (Florian Munteanu), it's the father burying the decades of hatred for Balboa and finally treating Viktor as a son instead of a tool for his revenge. For Adonis, it's escaping the shadow of his famous father and building his own legacy with the family he's having with Bianca (Tessa Thompson). And for Balboa, the time spent with Adonis makes him realize he has to finally reconnect with his son.

It's a storyline that wasn't addressed at all in the first "Creed" movie, but "Creed II" director Steven Caple Jr. said Stallone mentioned at their first meeting he wanted to bring back that storyline.

"He didn't want to die," Caple told Business Insider of how Stallone saw the Rocky character by the end of the sequel. "And we felt he needed his family, so Rocky had to leave Philly."

But the reuniting of Balboa and his son Robert (played by "This is Us" star Milo Ventimiglia, reprising the role he played in 2006's "Rocky Balboa") isn't the only shock "Rocky" fans find at the end of the movie. There's also how Balboa celebrates Creed's win over Drago. He never enters the ring.